The described invention relates in general to additive manufacturing systems and processes, and more specifically to systems, devices, and methods for characterizing, analyzing, and verifying the proper functioning and performance of lasers used in laser powder bed fusion manufacturing processes.
Additive manufacturing is an industrial process that enables the creation of components and devices that are stronger and lighter than those made by more traditional processes such as machining and casting. Additive manufacturing utilizes data computer-aided-design (CAD) software or 3D object scanners for directing system hardware to deposit and bond or fuse material, layer upon layer, in precise geometric shapes or patterns. As implied by its name, additive manufacturing adds successive superfine layers of material to create a three-dimensional object. Each successive layer bonds or is fused to a preceding layer of melted or partially melted material and different substances for layering material, including metal powder, thermoplastics, ceramics, composites, glass, and other materials may be used. Three-dimensional objects that are to be created are first digitally defined by computer-aided-design (CAD) software that is used to create specific digital files that essentially “slice” the modeled object into ultra-thin layers. This information is then used to guide the path of a nozzle, print head, or other device as it precisely deposits material upon a preceding layer. Alternately, an electron beam or laser may be used to selectively melt or partially melt powdered material. As the material layers cool or are cured, these layers fuse together to form the desired three-dimensional object.
Powder Bed Fusion (PBF) technology is used in a variety of additive manufacturing processes, including direct metal laser sintering (DMLS), selective laser sintering (SLS), selective heat sintering (SHS), electron beam melting (EBM) and direct metal laser melting (DMLM). These systems use lasers, electron beams or thermal print heads to melt and fuse ultra-fine layers of material powder for creating a part or component. PBF processes typically involve the spreading of powdered material over previously deposited layers of material using a roller, recoater arm, or coating blade, or the like. A hopper or a reservoir positioned below or next to the powder bed is used to provide fresh powdered material. As the process concludes, excess powder is blasted away from the object. Laser Powder Bed Fusion (L-PBF) is another additive manufacturing process in which a three-dimensional component or part is built using a layer-by-layer approach by utilizing a high-power laser. L-PBF typically involves the following general steps: (i) a layer of powdered material (e.g., metal), typically about 0.04 mm thick, for example, is spread over a build platform or plate; (ii) a laser fuses the first layer or first cross-section of the part; (iii) a new layer of powder is spread across the previous layer using a roller or similar device; (iv) further layers or cross sections are fused and added; and (v) the process is repeated until the entire part is created. Loose, unfused powdered material remains in position, but is removed during post processing.
The implementation and use of L-PBF for additive manufacturing applications has increased tremendously in recent times. Large numbers of L-PBF systems have been sold and installed worldwide, and the rate of these sales is increasing. The functional success of L-PBF systems depends on the existence of a known and stable laser focal spot on the powder bed work plane. However, an instrument or device for accurately measuring the laser focal spot in a dynamic manner, throughout the extent of the work place, does not currently exist. Accordingly, there is an ongoing need for an accurate, easy to use, affordable instrument for analyzing the quality and dynamic accuracy of laser focal spots in various L-PBF systems and devices. This type of analysis could conceivably be made a requirement for the commissioning and routine certification of many, if not all, metal L-PBF systems and devices.